Control unit, continuous-flow heater and method for controlling a continuous-flow heater

ABSTRACT

A control unit, a continuous-flow heater and a method, a flow rate of hot water through the continuous-flow heater being detected, a flow rate characteristic being ascertained on the basis of the detected flow rate over a period of time, the ascertained flow rate characteristic being compared in a comparison with a predefined characteristic, a heat output of the continuous-flow heater being controlled as a function of a result of the comparison.

FIELD OF THE INVENTION

The present invention relates to a control unit, a continuous-flow heater and a method relating thereto.

BACKGROUND INFORMATION

Continuous-flow heaters are believed to be understood which heat fresh water to produce hot water. The hot water is provided at a constant temperature to a faucet. Normally, the continuous-flow heater heats up to 60 degrees Celsius, in order to provide sufficiently hot water for both cleaning dishes and for showering. In order to achieve a sufficiently comfortable temperature for showering, the hot water is mixed with cold water at the faucet.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved control unit, an improved continuous-flow heater and an improved method.

This object is achieved with the aid of a control unit according to the description herein. Advantageous specific embodiments are specified in the further descriptions herein.

According to the present invention, it is believed that an improved control unit may be provided in that the control unit includes an interface, a control device and a memory. The control device is connected to the interface and the memory. A predefined characteristic is stored in the memory. The interface is connectable to a flow rate sensor of a continuous-flow heater. The interface is configured to detect a flow rate signal of the flow rate sensor and to provide it to the control device. The control device is configured to ascertain a flow rate characteristic on the basis of the flow rate signal over a period of time and in a comparison to compare the flow rate characteristic with the predefined characteristic. The control device is configured to provide a control signal at the interface for controlling a heat output of the continuous-flow heater as a function of the result of the comparison.

In this way, with a faucet present fitted with a thermostatic valve, which is usually situated in the bathroom, it may be detected that the user requires cooler warm water than that for cleaning dishes in the kitchen. As a result, the continuous-flow heater may be operated with greater efficiency in one operation.

In another specific embodiment, the predefined characteristic corresponds to a valve flow-through characteristic of a faucet. As a result, the utilization of this faucet may be detected and its operational behavior may be adapted as a function of the utilization of the faucet of the continuous-flow heater.

In another specific embodiment, the predefined characteristic includes a first time-delimited segment, a second time-delimited segment, and a third time-delimited segment. The second segment follows chronologically after the first segment and the third segment follows chronologically after the second segment. In the first segment, a predefined value is essentially constant over time. In the second segment, the predefined value essentially decreases over time. In the third segment, the predefined value is essentially constant over time and is lower than in the first segment.

In another specific embodiment, a tolerance range of the predefined characteristic is stored in the memory, the control device being configured to take the tolerance range into account in the comparison of the predefined characteristic with the ascertained flow rate characteristic.

In another specific embodiment, the interface is connectable to a temperature sensor and is configured to detect a temperature signal of the temperature sensor and provide it to the control device, the control device being configured to take the temperature signal into account when ascertaining the control signal.

The object is also achieved, however, by a continuous-flow heater according to the further descriptions herein. Advantageous specific embodiments are specified in the further descriptions herein.

According to the present invention, it is believed that an improved continuous-flow heater for providing hot water in a hot water system may be provided in that the continuous-flow heater includes a heat source, a flow rate sensor and a control unit. The control unit is configured as described above. The interface is connected to the flow rate sensor and to the heat source. The flow rate sensor is configured to detect a flow rate of hot water through the heat source and to provide a flow rate signal correlating with the flow rate through the heat source. The heat source is configured to detect the control signal provided at the interface and to adapt the heat output based on the detected control signal for heating the control unit.

In another specific embodiment, the control signal correlates with a first heat output of the heat source when the ascertained flow rate characteristic deviates from the predefined characteristic. When the ascertained flow rate characteristic coincides with the predefined characteristic, the control signal correlates with a second heat output of the heat source. The second heat output in this case is lower than the first heat output.

In another specific embodiment, at least one heat exchanger is provided. The heat source is configured as a burner, the heat exchanger including a first heat exchanger module having a first primary side, the first primary side being coupled to the heat source. The heat source is configured to combust a fuel for providing the heat output, an waste gas forming during the combustion of the fuel being guided to the primary side of the first heat exchanger module, the second heat output being selected in such a way that at least one component of the waste gas condenses at least partially on the first primary side. In this way, a condensation energy, in addition to the heat energy of the waste gas, may be guided into the secondary side of the heat exchanger to heat the hot water, so that the continuous-flow heater may operate particularly energy-efficiently.

In another specific embodiment, the first heat exchanger module includes a first secondary side, the first secondary side being connectable on the input side to a fresh water supply and on the output side to at least one faucet. The first heat exchanger module is configured on its secondary side to heat fresh water coming from the fresh water supply to produce hot water. A temperature sensor is also provided, the temperature sensor being situated on the output side of the first secondary side and being connected to the interface, the temperature sensor being configured to detect a temperature of the hot water on the output side of the heat exchanger and to provide a temperature signal correlating with the detected temperature to the interface. The control device is configured to control the heat output of the heat source as a function of the detected temperature and the detected flow rate.

In another specific embodiment, the heat exchanger includes a second heat exchanger module having a second primary side and a second secondary side. The first heat exchanger module includes a first secondary side, the first secondary side being thermally coupled to the second primary side of the second heat exchanger module, the second secondary side being connectable on the input side to a fresh water supply and on the output side to at least one faucet. The second heat exchanger module is configured on its secondary side to heat fresh water coming from the fresh water supply to produce hot water. A temperature sensor is also provided. The temperature sensor is situated on the output side of the second secondary side of the second heat exchanger module, and is connected to the interface, the temperature sensor being configured to detect a temperature of the hot water on the output side of the second heat exchanger module and to provide a temperature signal correlating with the detected temperature to the interface. The control device is configured to control the heat output of the heat source as a function of the detected temperature and of the detected flow rate.

The object is also achieved, however, by a method according to the descriptions herein. Advantageous specific embodiments are specified in the further descriptions herein.

According to the present invention, it is believed that an improved method for controlling a continuous-flow heater may be provided in that a flow rate of hot water through a continuous-flow heater is detected, a flow rate characteristic being ascertained on the basis of the detected flow rate over a period of time, in a comparison, the ascertained flow rate characteristic being compared with a predefined characteristic, a heat output of the continuous-flow heater being controlled as a function of the result of the comparison.

In another specific embodiment, a control signal correlating with a first heat output of the heat source is ascertained when the ascertained flow rate characteristic deviates from the predefined characteristic. When the ascertained flow rate characteristic coincides with the predefined characteristic, the control signal correlating with a second heat output of the heat source is ascertained. The second heat output in this case is lower than the first heat output.

The present invention is explained in greater detail below with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a depiction of a hot water system.

FIG. 2 schematically shows a depiction of a continuous-flow heater of the hot water system shown in FIG. 1.

FIG. 3 schematically shows a depiction of a faucet.

FIG. 4 shows a diagram of a predefined characteristic.

FIG. 5 shows a diagram with multiple variables plotted over a period of time.

FIG. 6 shows a diagram of a flow rate plotted over time.

FIG. 7 shows a flow chart of a method for controlling the hot water system.

FIG. 8 schematically shows a depiction of a hot water system according to another specific embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically shows a depiction of a hot water system 10 in a building 15. Hot water system 10 includes a continuous-flow heater 20, a first faucet 25 and a second faucet 30. First faucet 25 is situated, for example, in a bathroom 35 of building 15. Second faucet 30 is situated, for example, in a kitchen 40 of building 15. Additional faucets may, of course, also be provided.

Continuous-flow heater 20 includes an input side 41 and an output side 42. Input side 41 is connected via a first line 45 to a fresh water supply 50. Fresh water supply 50 provides fresh water 55. Fresh water 55 in this case has a low temperature, for example, in the range of 12 degrees, and is referred to below as cold water 56.

Output side 42 of continuous-flow heater 20 is connected via a line 60 to first faucet 25 and to second faucet 30. Furthermore, first faucet 25 is connected to fresh water supply 50 via a third line 65. Second faucet 30 is also connected to fresh water supply 50 via third line 65.

FIG. 2 schematically shows a depiction of continuous-flow heater 20 of hot water system 10 shown in FIG. 1. Continuous-flow heater 20 includes a control unit 70, a heat source 75, a heat exchanger 80, a flow rate sensor 85, and a temperature sensor 90. Heat exchanger 80 includes a heat exchanger module 81 having a primary side 95 and a secondary side 100. Primary side 95 is connected to heat source 75. Secondary side 100 is connected to input side 41 as well as to output side 42. Heat source 75 in the specific embodiment is configured as a burner, in particular, as a gas burner. Heat source 75 in this case is further connected to a fuel supply 105. Fuel supply 105 in this case provides a fuel 110. Fuel 110 in this case is combusted with atmospheric oxygen 112 in heat source 75 during the operation of continuous-flow heater 20. A waste gas 111 forming during the combustion of fuel 110 is guided to primary side 95 of heat exchanger module 81. A heat transfer of the heat from waste gas 111 takes place in heat exchanger module 81 from primary side 95 to secondary side 100. Waste gas 111, after flowing through primary side 95, is guided via a flue 115 of continuous-flow heater 20 out of continuous-flow heater 20.

Control unit 70 includes a control device 120, an interface 125 and a memory 130. Interface 125 is connected to control device 120 via a first connection 135. Memory 130 is connected to control device 120 via a second connection 140. Interface 125 is connected to heat source 75 via a third connection 145 and to flow rate sensor 85 via a fourth connection 150. Interface 125 is connected to temperature sensor 90 via a fifth connection 155. Temperature sensor 90 is configured to ascertain a temperature of fresh water 55 flowing from heat exchanger module 81. Temperature sensor 90 provides a correlating temperature signal corresponding to the detected temperature to interface 125 via fifth connection 155. Interface 125 relays the temperature signal to control device 120 via first connection 135. Flow rate sensor 85 detects flow rate f of fresh water 55 on the output side of heat exchanger module 81 in second line 60. Flow rate sensor 85 provides a flow rate signal corresponding to detected flow rate f. The flow rate signal is conducted via fourth connection 150 to interface 125, which provides the flow rate signal to control device 120 via first connection 135.

A predefined characteristic, a predefined first temperature threshold value T_(s1), a predefined second temperature threshold value T_(s2), as well as a first predefined flow rate threshold value f_(s1) and a second predefined flow rate threshold value f_(s2) are stored in memory 130. In this case, second flow rate threshold value f_(s2) is greater than first predefined flow rate threshold value f_(s1). First temperature threshold value T_(s1) is selected to be lower than second temperature threshold value T_(s2). First temperature threshold value T_(s1) may be 50° C., for example. Second temperature threshold value T_(s2) may be 60° C., for example. Also stored in memory 130 are a first setpoint value, for example, 60° C., and a second setpoint value, for example, 45° C.

A control parameter is also stored in memory 130 of control unit 70. The control parameter in this case includes a classification of a heat output as a function of a setpoint temperature and of ascertained flow rate f. The control parameter in this case may be configured as a tabular classification, as a characteristic diagram or as a mathematical formula. Furthermore, the control parameter may be expanded to the extent that the control parameter is configured as a control algorithm, which takes temperature T ascertained on the output side into account when ascertaining the heat output. Control device 120 ascertains a control signal formed corresponding to the heat output as a function of the ascertained heat output.

The provision of hot water to faucets 25, 30 will be only broadly described below, since it will be discussed in detail in the subsequent method. Pressurized fresh water 55 is provided in continuous-flow heater 20 via first line 45. If one of the two faucets 25, 30 is opened and hot water is required, then heat source 75 of continuous-flow heater 20 is activated. Fresh water 55 is heated in secondary side 100 and flows as fresh water 55 at a temperature greater than the temperature of cold water 56 as hot water 57 from secondary side 100 via output side 42 into second line 60.

FIG. 3 schematically shows a depiction of first faucet 25. First faucet 25 includes a first connection 160 and a second connection 165. First faucet 25 is connected via first connection 160 to second line 60. First faucet 25 is connected via second connection 165 to third line 65. First faucet 25 further includes a third connection 170. A shower hose 175, for example, may be attached to third connection 170. It is also conceivable that, in addition or alternatively to a third connection 170, an outlet is provided for filling a bathtub or a sink or for connecting to a household appliance, for example, a washing machine or a dishwasher.

First faucet 25 in the specific embodiment includes a, for example, cylindrically configured housing 176. Housing 176 includes an inner chamber 117. Inner chamber 177 is fluidically connected to second connection 165.

First faucet 25 includes a temperature control device 180. Temperature control device 180 includes a temperature valve 185, a temperature valve actuation element 190 and a temperature pre-selection element 195. Temperature pre-selection element 195 is situated in the specific embodiment on the left side on housing 176 and is coupled to temperature valve 185. Temperature valve 185 is fluidically situated between inner chamber 177 and first connection 160. First faucet 25 further includes an opening valve 200. Opening valve 200 is situated in the specific embodiment on the right side of housing 176 and is fluidically situated between inner chamber 177 and third connection 170.

Second faucet 30 may be configured as a conventional mixing faucet, for example, as a single lever mixer. These are normally used in the kitchen, since on the one hand a higher flow velocity for washing dishes is advantageous for the user and, on the other hand, these are particularly easy to operate and to quickly open and close.

First faucet 25 as well as second faucet 30 are used to tap fresh water 55 having a different temperature. Here, the user in bathroom 35, in particular, in the shower, is far more sensitive to temperature than when dishes are rinsed. Furthermore, when washing dishes in kitchen 40, fresh water 55 having a temperature higher than fresh water 55 tapped via first faucet 25 for showering/bathing/washing, is normally used in order to easily remove residue, such as grease, from kitchenware. Furthermore, hot water 57 having a particularly high temperature, for example, 60 degrees, is tapped via second faucet 30 in order to clean floors of building 15.

Fresh water 55 tapped from first faucet 25 should normally have a constant temperature, which is lower than fresh water 55 tapped at second faucet 30. Based on experience, fresh water 55 having a temperature of 36° C. to 39° C. is tapped at first faucet 25.

To tap fresh water 55 from first faucet 25, a desired tapping temperature, for example, 38° C., is set by the user on temperature pre-selection element 195. In addition, the user opens first faucet 25 with the aid of opening valve 200, so that fresh water 55 flows from first faucet 25 via third connection 170.

At the start of a temperature control operation by temperature control device 180, temperature valve 185 is in the wide opened state. As a result, cold fresh water 55 flows via first connection 160 from second line 60 and cold water 56 flows via second connection 165 into inner chamber 177. Fresh water 55 initially flowing in from second line 60 normally has a lower temperature than hot water 57 flowing out of continuous-flow heater 20. In inner chamber 177, cold water 56 is mixed with fresh water 55 originating from second line 60 to produce warm water 178. Depending on the temperature of warm water 178, temperature valve actuation element 190 shifts temperature valve 185 as a function of the desired temperature set by the user with the aid of temperature pre-selection element 195, in order to provide warm water 178 at the desired temperature at third connection 170.

Warm water 178 tappable at faucet 25, 30 is produced at faucets 25, 30 by mixing hot water 57 supplied via second line 60 with cold water 56 supplied via third line 65. Continuous-flow heater 20 is activated if warm water 178 is required. If warm water 178 is no longer required at faucet 25, 30, then faucet 25, 30 is closed and continuous-flow heater is deactivated.

FIG. 4 shows a diagram of a predefined characteristic stored in memory 130. The predefined characteristic corresponds to a valve flow rate characteristic of first faucet 25.

The predefined characteristic in the specific embodiment includes, for example, three graphs 300, 305, 310. Here, a first graph 300 correlates to a flow rate f of fresh water 55 through continuous-flow heater 20, plotted over a time t from the start of the tapping of fresh water 55 at first faucet 25 with a constant tapping of warm water 178 at first faucet 25 for example, for first graph 300 of 10.2 l/min. A second graph 305 correlates with a second flow rate f from the start of the tapping of fresh water 55 at first faucet 25 with a constant tapping of warm water 178 at first faucet 25, for example, for second graph 305 of 8 l/min. A third graph 310 correlates with a third flow rate f from the start of the tapping of fresh water 55 at first faucet 25 with a constant tapping of warm water 178 at first faucet 25, for example, for third graph 310 of 7 l/min. It is also conceivable, of course, that the predefined characteristic includes additional graphs. It is also conceivable that the predefined characteristic is stored in memory 130, not as a graph, but rather as a mathematical function or parameterized.

FIG. 5 shows a diagram with multiple variables plotted over time t. A fourth graph 350, a fifth graph 355, a sixth graph 360 and a seventh graph 365 are depicted in the diagram. Fourth graph 350 shows the temperature of hot water 57 on output side 42 of continuous-flow heater 20 in decimal degrees Celsius (dC). Fifth graph 355 shows a temperature curve of warm water 178 at third connection 170 in decimal degrees Celsius. Sixth graph 360 corresponds to first graph 300 shown in FIG. 4 and corresponds to a flow rate f of hot water 57 through continuous-flow heater 20 in deciliters at a tapping of, for example, 10.2 l/min of warm water 178 at first faucet 25. Seventh graph 365 shows an output P delivered by continuous-flow heater 20 in percentage relative to a maximum output of continuous-flow heater 20.

First graph 300 is explained below by way of example for additional graphs 305, 310. First graph 300 correlates with a control behavior of temperature control device 180 of first faucet 25. First graph 300 of the predefined characteristic includes a first time-delimited segment 315, a second time-delimited segment 320 and a third time-delimited segment 325. First segment 315 is delimited initially by a start 330 of the tapping. An end of first segment 315 is delimited by second segment 320. Third segment 325 is delimited initially by an end of second segment 320. Third segment 325 may theoretically be infinitely long chronologically, however, the characteristic in the specific embodiment has a predefined duration which, in the specific embodiment, is 35 seconds, for example. In first segment 315, first graph 300 has a predefined value, which is essentially constant over time t. In second segment 320, the predefined value decreases from the value in first segment 315. In third segment 325, the predefined value is essentially constant over time t. Here, the predefined value in third segment 325 is lower than in first segment 315.

The control behavior of first faucet 25 corresponding to the predefined characteristic in individual segments 315, 320, 325 is explained below.

At the start of a tapping of fresh water 55 from first faucet 25, temperature valve 185 is completely opened. The tapping from first faucet 25 starts with the opening of opening valve 200. In the process (cf. first segment 315), fresh water 55 at a low temperature, which is cooled in second line 60 over time t prior to the tapping, flows from second line 60 into inner chamber 177, where it is mixed with cold water 56 coming from third line 65. The admixed water has a temperature, which is lower than the set desired temperature, so that in first segment 315, flow rate f is constant over time t. The temperature of cold water 56 is essentially constant over the tapping.

As explained above, continuous-flow heater 20 is activated with the tapping of fresh water 55 from second line 60. In second segment 320, fresh water 55 subsequently flowing via second line 60 has a higher temperature with increasing time t until fresh water 55 reaches first faucet 25 as hot water 57. The increasingly warming fresh water 55 is mixed in inner chamber 177 with cold water 56 to produce warm water 178. Warm water 178 heats temperature valve actuation element 190, which then actuates temperature valve 185 and reduces the inflow of hot water 57 via first connection 160 over time t. As a result, flow rate f in second segment 320 decreases over time t. The reduction of flow rate f also causes a temperature increase in hot water 57 (cf. fourth graph 350). As a result, temperature valve actuation element 190 closes temperature valve 185 further over time t, so that flow rate f through heat exchanger module 81 decreases further until an equilibrium is established between flow rate f and the temperature of hot water 57 in third segment 325 following second segment 320 and flow rate f is constant over time t.

FIG. 6 shows a diagram of flow rate f plotted over time t as fresh water 55 is tapped via second faucet 30. The curve of flow rate f over time t is not, as explained in FIG. 5, due to the control behavior of temperature control device 180, but rather is arbitrary and a function of how the user operates second faucet 30. Thus, the tapping of fresh water 55 via second faucet 30 does not have the characteristic shown in FIG. 4.

FIG. 7 shows a flow chart of a method for operating hot water system 10 described in FIGS. 1 through 3.

In a first method step 400, control device 120 checks whether continuous-flow heater 20 is in the stand-by mode. If this is the case, control device 120 continues with a second method step 405. If this is not the case, control device 120 waits until continuous-flow heater 20 is activated.

In a second method step 405, control device 120 checks whether heat source 75 is activatable. If this is the case, control device 120 continues with a third method step 410. If this is not the case, control device 120 waits to see whether heat source 75 is activatable.

In a third method step 410, control device 120 detects the temperature signal and the flow rate signal.

Control device 120 compares detected temperature T on the output side of heat exchanger module 81 with first temperature threshold value T_(s1) in a first comparison. If temperature T exceeds first temperature threshold value T_(s1), then control device 120 continues with a fourth method step 415. If detected temperature T falls below first temperature threshold value T_(s1), then control device 120 waits until temperature T exceed first temperature threshold value T_(s1).

In fourth method step 415, control device 120 compares in a second comparison detected flow rate f with first flow rate threshold value f_(s1) and with second flow rate threshold value f_(s2).

If ascertained flow rate f exceeds first flow rate threshold value f_(s1) and ascertained flow rate f falls below second flow rate threshold value f_(s2), then control device 120 continues with a fifth method step 420. If ascertained flow rate f falls below first flow rate threshold value f_(s1) or ascertained flow rate f exceeds second flow rate threshold value f_(s2), then control device 120 continues with a sixth method step 425.

In fifth method step 420, control device 120 compares in a third comparison ascertained temperature T with second temperature threshold value T_(s2). If ascertained temperature T falls below second temperature threshold value T_(s2), then control device 120 waits until ascertained temperature T is greater than or equal to second temperature threshold value T_(s2). If ascertained temperature T exceeds second temperature threshold value T_(s2), then control device 120 continues with a seventh method step 430.

In a sixth method step 425, control device 120 selects the first setpoint value as the setpoint temperature for ascertaining the control signal for controlling the heat output of heat source 75. As a function of the first setpoint value, control device 120 ascertains a first control signal on the basis of the control parameter, which correlates with a first heat output P₁ and provides the first control signal to heat source 75 via interface 125. Heat source 75 detects the first control signal. Heat source 75 is controlled with the aid of the first control signal in such a way that the heat source delivers first heat output P₁ and fresh water 55 flowing out on the output side from heat exchanger module 81 exhibits essentially the temperature of the first setpoint value.

In a seventh method step 430, control device 120 assigns detected flow rate f time t from the start of the tapping and stores the detected value of flow rate f with assigned time t in memory 130. Control device 120 ascertains a flow rate characteristic of flow rate f over time t on the basis of the values for flow rate f stored in memory 130. In a fourth comparison, control device 120 compares the ascertained flow rate characteristic with the predefined characteristic. Thus, for example, the ascertained flow rate characteristic may coincide with first graph 300, with second graph 305 or with third graph 310, depending on how wide opening valve 200 is opened.

A tolerance range may also be stored in memory 130, which control unit 120 takes into account during the fourth comparison of the ascertained flow rate characteristic with the predefined characteristic, so that a deviation of the ascertained flow rate characteristic is assignable by control device 120 to the corresponding predefined characteristic. In this way, a tapping of fresh water 55 from first faucet 25 may be reliably detected.

If fresh water 55 is tapped from first faucet 25, then the flow rate characteristic ascertained, for example, by control device 120 corresponds to the curve of flow rate f over time t shown in FIG. 5, but not to the predefined characteristic.

If the ascertained flow rate characteristic coincides with the predefined characteristic, then control device 120 continues with eighth method step 435. If the ascertained flow rate characteristic does not coincide with the predefined characteristic, then control device 120 continues with sixth method step 425.

In eighth method step 435, control device 120 selects the second setpoint value as the second setpoint temperature which, in the specific embodiment, is 45° C. In addition, control device 120 may, if the setpoint temperature value was the first setpoint value during a previous run-through of the described method, continuously lower this first setpoint value in eighth method step 435 on the basis of a predefined lowering parameter. Thus, it is conceivable, for example, to lower the setpoint temperature value over time t from the first setpoint value down to the second setpoint value by 1° C. every 100 milliseconds. As a function of the second setpoint value, control device 120 ascertains on the basis of the control parameter a second control signal, which correlates with a second heat output P₂, and provides the second control signal to heat source 75 via interface 125. Heat source 75 detects the second control signal. Heat source 75 is controlled with the aid of the second control signal in such a way that the heat source delivers second heat output P₂ and fresh water 55 flowing out on the output side from heat exchanger module 81 exhibits essentially the temperature of the second setpoint value.

If control device 120 establishes the second setpoint value as the setpoint temperature value, this means then that when second heat output P₂ is delivered by heat source 75, the waste gas 111 forming during combustion of fuel 110 when guided through primary side 95 condenses in heat exchanger module 81 at least partially on primary side 95. This has the advantage that, in addition to the heat energy, a condensation energy may be utilized to heat fresh water 55 in secondary side 100 of heat exchanger module 81. In this way, the efficiency of continuous-flow heater 20 may be further increased.

In a ninth method step 440 following eighth method step 435, control device 120 compares in a fifth comparison flow rate f with second predefined flow rate threshold value f_(s2). If flow rate f exceeds predefined second flow rate threshold value f_(s2), the method is continued by a tenth method step 445 by control device 120. If flow rate f falls below predefined second flow rate threshold value f_(s2), the method is continued by an eleventh method step 450.

In a tenth method step 445, the first setpoint value is established as the setpoint temperature value, so that fresh water 55 flowing through heat exchanger module 81 is heated more intensively and may be tapped via second faucet 30 at a temperature of 60° C. In addition, control device 120 may, if the setpoint temperature value was the second setpoint value during a previous run-through of the described method, continuously raise this second setpoint value in tenth method step 445 on the basis of a predefined raising parameter. Thus, it is conceivable, for example, to raise the setpoint temperature value over time t from the second setpoint value up to the first setpoint value by 5° C. every 100 milliseconds.

In the eleventh method step 450, the second setpoint value is established as the setpoint temperature value.

Following eleventh method step 450 is a twelfth method step 455, in which it is checked whether flow rate f equals zero. If this is not the case, control device 120 continues with ninth method step 440. If this is the case, control device 120 continues with a thirteenth method step 460.

In thirteenth method step 460, the setpoint temperature value is set to the first setpoint value and thus, for example, at 60 degrees in the specific embodiment. Thirteenth method step 460 is followed by first method step 400.

Following tenth method step 445 is a fourteenth method step 465. In fourteenth method step 465, control device 120 compares in a sixth comparison whether detected temperature T, like the setpoint temperature value, corresponds with the first setpoint value. If this is the case, control device 120 continues with a fifteenth method step 470. If this is not the case, the control device repeats tenth method step 445.

In fifteenth method step 470, control device 120 checks whether flow rate f equals zero. If this is the case, control device 120 continues with thirteenth method step 460. If this is not the case, fifteenth method step 470 is repeated.

It is noted that additional method steps may, of course, be provided and/or the above described method steps may be carried out in a different sequence.

FIG. 8 schematically shows a depiction of a hot water system 10 according to another specific embodiment.

Hot water system 10 is configured similarly to hot water system 10 shown in the preceding figures. In contrast to the latter, heat exchanger 80 is constructed in multiple parts and includes a first heat exchanger module 499 and a second heat exchanger module 500. First heat exchanger module 499 is configured essentially identical to heat exchanger module 81 described in FIGS. 1 through 7. First heat exchanger module 499 includes a first primary side 501 and a first secondary side 502. First primary side 501 corresponds to primary side 95 of heat exchanger module 81 described in FIGS. 1 through 7.

Second heat exchanger module 500 includes a second primary side 505 and a second secondary side 510. Second heat exchanger module 500 in the specific embodiment is configured as a counterflow heat exchanger. Other embodiments of the second heat exchanger module are, of course, also conceivable such as, for example, as a cross-flow heat exchanger or as a parallel flow heat exchanger 500.

In contrast to FIGS. 1 through 7, first secondary side 502 of first heat exchanger module 499 is fluidically connected on the output side by a fourth line 515 to second primary side 505 of second heat exchanger module 500. On the input side, first secondary side 502 of first heat exchanger module 499 is fluidically connected to second primary side 505 of second heat exchanger module 500 via a fifth line 520. Fourth line 515, fifth line 520 and second primary side 505 of second heat exchanger module 500 and, in contrast to the preceding figures—first secondary side 502 of first heat exchanger module 499 are filled with a heat transfer medium 525, which may include water, for example. As a result, first secondary side 502 is thermally coupled with second primary side 505 of second heat exchanger module 500.

In contrast to FIGS. 1 through 7, second secondary side 510 of second heat exchanger module 500 is connected on the input side to input side 41 of continuous-flow heater 20 and, therefore, to fresh water supply 50 via first line 45. On the output side, second secondary side 510 of second heat exchanger module 500 is connected to output side 42 of continuous-flow heater 20 and, therefore, to second line 60. In this case, flow rate sensor 85 and temperature sensor 90 are situated on the output side of second secondary side 510, temperature sensor 90 being connected to interface 125, temperature sensor 90 being configured to detect a temperature T of hot water 57 on the output side of second heat exchanger module 500 and to provide a temperature signal to interface 125 correlating with detected temperature T. Flow rate sensor 85 detects the flow rate of cold fresh water 55 and/or fresh water 55 heated to produce hot water 57 through second secondary side 50 of second heat exchanger module 500 and provides the flow rate signal correlating with flow rate f to interface 125.

Furthermore, it is also conceivable, as shown by way of example in FIG. 8, that fourth line 515 and fifth line 520 are connected to a heating circuit 530 for heating a building 15. For this purpose, a valve 535 may also be provided in fifth line 520, in order to separate heating circuit 530 fluidically from fifth line 520. A feed pump 540 is further provided, for example, in fifth line 520 for feeding heat transfer medium 525. Feed pump 540 may, of course, alternatively also be situated in fourth line 515.

The operation of continuous-flow heater 20 is similar to the method described in FIGS. 1 through 7. In contrast thereto, heat transfer medium 525 and not fresh water 55, as described in FIGS. 1 through 7, is heated in first heat exchanger module 81. Heated heat transfer medium 525 is conveyed by feed pump 540 via fourth line 515 to second primary side 505 of second heat exchanger module 500. In second heat exchanger 500, heat transfer medium 525 dissipates at least a part of its heat for heating fresh water 55 present in second secondary side 510 to hot water 57. Cooled heat transfer medium 525 flows via fifth line 520 back to first secondary side 502 of first heat exchanger module 499. Control device 120 controls heat output P of heat source 75 as described above as a function of the temperature signal and of the flow rate signal. In this case, control device 120 may also provide an additional control signal for activating feed pump 540 when detecting a tapping of hot water 57 via at least one of the two faucets.

The embodiment of continuous-flow heater 20 described in FIG. 8 has the advantage that heat source 75, in addition to heating fresh water 55 to produce hot water 57, may further be utilized to heat heating circuit 530. Heat source 75 may further be situated spatially separated from second heat exchanger module 500, so that the installation space requirement of continuous-flow heater 20 is adaptable.

It is further conceivable that second primary side 505 of second heat exchanger module 500 is connected to an additional heat source (not depicted). The additional heat source in this case may be configured, for example, as a thermal solar collector. Here, too, it is advantageous that heat source 75 in conjunction with second heat exchanger module 500 may be operated with less output P when detecting the tapping of warm water 178 at first faucet 25, so that the efficiency of continuous-flow heater 20 is increased. 

1-12. (canceled)
 13. A control unit for a continuous-flow heater, comprising: an interface; a control device; and a memory; wherein the control device is connected to the interface and to the memory, wherein a predefined characteristic is stored in the memory, wherein the interface is connectable to a flow rate sensor of the continuous-flow heater, wherein the interface is configured to detect a flow rate signal of the flow rate sensor and to provide it to the control device, wherein the control device is configured to ascertain a flow rate characteristic based on the flow rate signal over a time and to compare the flow rate characteristic with the predefined characteristic, and wherein the control device is configured to provide a control signal for controlling a heat output of the continuous-flow heater at the interface as a function of a result of the comparison.
 14. The control unit of claim 13, wherein the predefined characteristic corresponds to a valve flow rate characteristic of a faucet.
 15. The control unit of claim 13, wherein the predefined characteristic includes a first time-delimited segment, a second time-delimited segment and a third time-delimited segment, wherein the second segment follows chronologically the first segment and the third segment follows chronologically the second segment, wherein a predefined value over the time is essentially constant in the first segment, wherein the predefined value essentially decreases over the time in the second segment, and wherein the predefined value is essentially constant over the time in the third segment and is lower than in the first segment.
 16. The control unit of claim 13, wherein a tolerance range of the predefined characteristic is stored in the memory, and wherein the control device is configured to take the tolerance range into account in the comparison of the predefined characteristic with the ascertained flow rate characteristic.
 17. The control unit of claim 13, wherein the interface is connectable to a temperature sensor and is configured to detect a temperature signal of the temperature sensor and to provide it to the control device, and wherein the control device is configured to take the temperature signal into account when ascertaining the control signal.
 18. A continuous-flow heater for providing hot water in a hot water system, comprising: a heat source; a flow rate sensor; and a control unit; wherein the control unit control unit includes an interface, a control device; and a memory, wherein the control device is connected to the interface and to the memory, wherein a predefined characteristic is stored in the memory, wherein the interface is connected to a flow rate sensor of the continuous-flow heater, wherein the interface is configured to detect a flow rate signal of the flow rate sensor and to provide it to the control device, wherein the control device is configured to ascertain a flow rate characteristic based on the flow rate signal over a time and to compare the flow rate characteristic with the predefined characteristic, and wherein the control device is configured to provide a control signal for controlling a heat output of the continuous-flow heater at the interface as a function of a result of the comparison, wherein the interface is connected to the heat source, and wherein the flow rate sensor is situatable on the output side of a heat exchanger thermally coupleable to the heat source, wherein the flow rate sensor is configured to detect a flow rate of hot water through the heat exchanger and to provide a flow rate signal correlating with the flow rate through the heat source, and wherein the heat source is configured to detect the control signal provided at the interface and to adapt the heat output for heating the hot water based on the detected control signal.
 19. The continuous-flow heater of claim 18, wherein the control signal correlates with a first heat output of the heat source when the ascertained flow rate characteristic deviates from the predefined characteristic, wherein the control signal correlates with a second heat output of the heat source when the ascertained flow rate characteristic coincides with the predefined characteristic, and wherein the second heat output is lower than the first heat output.
 20. The continuous-flow heater of claim 19, wherein there is at least one heat exchanger and the heat source includes a burner, wherein the heat exchanger includes a first heat exchanger module having a first primary side, wherein the first primary side is coupled to the heat source, wherein the heat source is configured to combust a fuel for providing the heat output, wherein a waste gas formed during the combustion of the fuel is guided to the first primary side of the first heat exchanger module, and wherein the second heat output is selected so that at least one component of the waste gas condenses at least partially on the first primary side.
 21. The continuous-flow heater of claim 20, wherein the first heat exchanger module includes a first secondary side, wherein the first secondary side is connectable on the input side to a fresh water supply and on the output side to at least one faucet, wherein the first heat exchanger module is configured on its first secondary side to heat fresh water coming from the fresh water supply to produce hot water, wherein a temperature sensor is situated on the output side of the first secondary side and is connected to the interface, and wherein the temperature sensor is configured to detect a temperature of the hot water on the output side of the heat exchanger and to provide a temperature signal correlating with the detected temperature to the interface, and wherein the control device is configured to control the heat output of the heat source as a function of the detected temperature and of the detected flow rate.
 22. The continuous-flow heater of claim 20, wherein the heat exchanger includes a second heat exchanger module having a second primary side and a second secondary side, wherein the first heat exchanger module includes a first secondary side, wherein the first secondary side is thermally coupled to the second primary side of the second heat exchanger module, wherein the second secondary side is connectable on the input side to a fresh water supply and to at least one faucet on the output side, wherein the second heat exchanger module is configured to heat fresh water coming from the fresh water supply to produce hot water on its second secondary side, wherein a temperature sensor is situated on the output side of the second secondary side of the second heat exchanger module and is connectable to the interface, wherein the temperature sensor is configured to detect a temperature of the hot water on the output side of the second heat exchanger module and to provide a temperature signal correlating with the detected temperature to the interface, and wherein the control device is configured to control the heat output of the heat source as a function of the detected temperature and of the detected flow rate.
 23. A method for controlling a continuous-flow heater device, comprising: a continuous-flow heater including: a heat source; a flow rate sensor; and a control unit; wherein the control unit control unit includes an interface, a control device; and a memory, wherein the control device is connected to the interface and to the memory, wherein a predefined characteristic is stored in the memory, wherein the interface is connected to a flow rate sensor of the continuous-flow heater, wherein the interface is configured to detect a flow rate signal of the flow rate sensor and to provide it to the control device, wherein the control device is configured to ascertain a flow rate characteristic based on the flow rate signal over a time and to compare the flow rate characteristic with the predefined characteristic, and wherein the control device is configured to provide a control signal for controlling a heat output of the continuous-flow heater at the interface as a function of a result of the comparison, wherein the interface is connected to the heat source, and wherein the flow rate sensor is situatable on the output side of a heat exchanger thermally coupleable to the heat source, wherein the flow rate sensor is configured to detect a flow rate of hot water through the heat exchanger and to provide a flow rate signal correlating with the flow rate through the heat source, and wherein the heat source is configured to detect the control signal provided at the interface and to adapt the heat output for heating the hot water based on the detected control signal; wherein a flow rate of hot water through a continuous-flow heater is detected, wherein a flow rate characteristic is ascertained based on the detected flow rate over a time, wherein the ascertained flow rate characteristic is compared in a comparison with a predefined characteristic, and wherein a heat output of the continuous-flow heater is controlled as a function of a result of the comparison.
 24. The method of claim 23, wherein a control signal correlates with a first heat output of the heat source which is ascertained when the ascertained flow rate characteristic deviates from the predefined characteristic, wherein the control signal correlates with a second heat output of the heat source which is ascertained when the ascertained flow rate characteristic coincides with the predefined characteristic, and wherein the second heat output is lower than the first heat output. 